Gale Warning 91, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
250 PM AKDT Sat Mar 21 2020

.SHORT TERM...Short term forecast is broken up into two parts.
First one has a developing low over the northern gulf Saturday
afternoon will track southeast to be near Haida Gwaii midday
Sunday. This timing is slightly slower than what was being seen
earlier. Rain and/or snow will spread across the Northeast Gulf
Coast this evening and then shift east-southeast over the
panhandle overnight and Sunday. Best rainfall totals look to fall
along the outer coast of a half inch to an inch of rain. Locally
moderate to heavy for a few hours as the band of the heavier
slides through the area.

White Pass will stay as snow above 900ft with about 3 inches of
accumulation. Precipitation ends from the west northwest and as
the low moves further south by Sunday night the southern panhandle
will be drying as well. Cooler dry air behind the low and system
aloft may try and change some the precipitation at the end of the
event to snow or at least a mix. After it ends expect to see
clearing conditions for the gulf and panhandle.

The second part of the forecast happens after the low goes by to
the southern part of the panhandle. High pressure is building
through the interior of Alaska to northwest Canada. The gradient
will quickly develop through Sunday and Sunday night, so the
northerly outflow will start and increase.

Winds over Lynn Canal increasing to gale force, and some cooler
and drier air will be making way towards the northeast Gulf of
Alaska. Overnight lows cooling to the mid to upper 20s or lower
30s, but daytime heating, now with longer days and increased sun
angle, will help keep the daytime numbers up with the sunshine
rising into the the 40s.

.LONG TERM.../Monday through Friday night/...A weak low will be
located over Vancouver Island with an inverted trough extending
northwest along the outer coast by Monday morning. Precipitation
associated with the low will have ended by the start of this
extended range forecast period. High pressure from the interior of
Alaska will have spread east and begun to sag south. The
combination of the inverted trough and the high pressure to the
north will produce a strong northerly gradient and result in
another outflow event for Southeast Alaska. Gradient numbers are
looking a bit stronger than last night, so have increased winds
over Lynn Canal to 40 kts for Monday. A combination of a weakening
inverted trough and diminishing high pressure still look like this
outflow event will be short lived - over by Tuesday morning. Thus
far, very little change from the previous long range forecast.
Model agreement past Tuesday night with respect to the next round
of precipitation is pathetic, so no changes there either and the
PoP forecast has been made with a very broad brush from Wednesday
onward and lacks any spatial or temporal detail.

What has changed in this long term forecast is the likelihood of
another southerly excursion by the Arctic front. Colder than
normal low level air over the eastern gulf and Southeast Alaska
will be shifted east by Wednesday morning. However, by Thursday
afternoon cold air will drop out of the Yukon and advect south
over the Gulf. At the same time, the Arctic front - oriented
northwest to southeast - will drop south and press up upon the
Canadian side of the Coast Mountains. Still too early to
determine if this will be a significant wind event, but it does
look like we are in for some more very winter-like temperatures
and snow as we make out way through the last week of March.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind Sunday afternoon for AKZ022.
     Strong Wind from Sunday morning through Sunday afternoon for
     AKZ018.
MARINE...Gale Warning for PKZ012-013.
     Small Craft Advisory for PKZ011-021-022-031>034-041>043-051-052.

&&

Bezenek/Fritsch

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